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wiring solar panels in series or parallel?
If my roof gets shaded during part of the day should I wire my panels in series or parallel?
Replies to This Discussion
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Permalink Reply by Deep Patel on -
wiring your solar panels in series or parallel is not going to make a difference in your performance loss due to shading. When a string of solar panels are partly shaded, the entire performance of the solar panel array will decrease. To determine how to wire your solar panels in series or parallel will depend on a couple factors:
#1 - the voltage of each solar panel
#2 - the inverter you are using
#3 - ambient temperatures in your area
You should first goto the inverter manufactures website or use PVSelect.com to determine the optimal string configuration based on your solar panel, inverter and ambient temperatures you experience in your region.
If there is no way you can avoid shading, I would recommend you use Enphase Micro-Inverters for the entire system or if you want to stick with a central inverter then pickup a Power Optimizer such as SolarMagic and install it on the string that has shading issues.
Does this help?
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Permalink Reply by Martin Herzfeld on -
Besides the area requirements - shade is the substantial issue for any photovoltaic installation. A commercial roof or a residential roof - what are the area requirements?
It is best practice to maximize the photovoltaic source circuits based on the highest V(oc) for the lowest ambient temperature if using a sting inverter - maximize the number of modules. Over the long term with regards to light induced degradation (LID), the array is likely to continue to achieve start voltages and maximum power point tracking (MPPT). One of the factors is if E/W or N/S shading whether landscape or portrait. For residential applications suggest the use of Crystalline and Multicrystalline Silicon Modules, although other people may install thin film for residential applications and the technology provides some shade mitigation in addition in a hope to extend the solar day. Appears continued development to MPP tracking for thin film could perform substantially better with one inverter than another of the various inverter manufactures. Both micro-inverters and macro-inverters have efficiency curves which may be optimized if relative V(oc) is maximized.
Micro-inverters: "If there is no way you can avoid shading, I would recommend you use Enphase Micro-Inverters" With micro-inverters, minimize shading impacts in individual modules - Crystalline and Multicrystalline Silicon Modules. Using compatible modules types with micro-inverters minimizes the impact of shading, than a greater area required for the use of thin film - right? If cost is an issue, then consider and choose a module with another STC at lower relative cost? ~ < 3kW - with options for larger sizes at the point of connection on the load side - developing on the supply side options.
http://www.enphaseenergy.com/downloads/Enphase_Module_Compatibility...
http://www.gogreensolar.com/collections/solar-panels
http://www.gogreensolar.com/products/enphase-energy-micro-inverter-...
Macro-inverters: With traditional inverters, relative high V(oc) for each photovoltaic source circuit - maximize number of modules, is more than one, minimize to at least that one. If cost is an issue, then consider and choose a module with a another STC at lower relative cost? ~ > 3kW with options for larger sizes at the point of connection on the supply and load side. "Power Optimizer such as SolarMagic and install it on the string that has shading issues." If you are considering the DC/DC products then each unit would be required along the entire photovoltaic source circuit and as of yet monitoring of each of the units now appears unavailable as an option or a feature. The pricing of the DC/DC products appears to be equivalent to the DC/AC micro-inverter products. If there array is substantially larger, options could be determined. For larger roof top arrays, thin film may be an option.
A note on definitions, in accordance to NEC 690.2 definitions, "Module. A complete, environmentally protected unit consisting of solar cells" and a "Panel. A collection of modules mechanically fastened together." Therefore, a cell < module < panel < ... typically a 'panel' is connected in parallel and a 'module' in series' for a panel. Experts in the industry use the terms interchangeable - including module manufacture data sheets and really "not going to make a difference in your performance" - shading.
Actually, NEC 690.64 is appears to be developing on both - load and supply. Series or parallel would be respective also of inverter type also :)! What is one module per inverter:)?
One you can, the other already is, the other you shouldn't and the other is what you should do.
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Permalink Reply by Alexandra Lipsitz on
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I am novice- so most of what you said went right over my head sadly-= guess this is why if you are broke and cant hire a pro it is to complicated to put in a solar system.
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Permalink Reply by Martin Herzfeld on
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Alexandra: You are correct. Solar really is simple, really. No sun, no solar.
Let's start with steps - 4, and no more.
1. Find a place with good sunlight. If you wish to learn, suggest Solar Pathfinder and develop some skills and stick a pole in the ground, if on the ground.
If you have no skills as an owner builder, then suggest a solar integrator. If on the roof, suggest contact a roofer which also does photovoltaics (PV).
2. If you have skills, select a module you like from the module list:
http://www.enphaseenergy.com/downloads/Enphase_Module_Compatibility.
http://www.gogreensolar.com/collections/solar-panels
3. If you have skills, purchase an inverter and a module - suggest micro-inverter.
http://www.gogreensolar.com/products/enphase-energy-micro-inverter-...
4. Call an electrician or a roofer which also does solar and ignore your question of series or parallel, as Deep said "wiring your solar panels in series or parallel is not going to make a difference in your performance" If, no sun, no fun. Let's talk about the money. The cost should be approximately $1000 * number of modules * 1.56 as the installed cost of 1 module with 1 inverter should cost approximately $1560 up to, let say, up to 12 modules or more.
If you have no skills, no money, no solar? Wish more people or the government would provided solar equipment to each other as a gift or holiday present - if you have people who care. Give someone a solar module and inverter. Solar modules are given as anniversary presents. One module inverter for each month of the year. Solar make great gifts. "Energy is a Human Right." as http://www.self.org/ and some others. And solar really, empowers people. Which happens to be as a factor of time! 'emergy' = empower * time - maximum empower defined as prevalence.
In other words, in time you will learn and prevail. What do you think?
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Sounds good- love ot be empowered. Wish my solar godmother would come along, But for now I guess I will read up on the micro inverter, all I know is folks have suggested I get an Epanel with an MPPT charge controller for 4 6volt batteries in series and a big inverter that can handle 2600 watts. This plus 2 panels..it starts to add up. During hte summer I get full sun its just when the winter comes and the sun is not so high in the sky we get these things called shadows from big redwood trees near by- no chance on them going away and the house is not moving - nor do I want to. So there it is. Someone told me if you get shade on one panel then the one that is in full sun stops making power - so not to run them in series and go parallel into the mppt charge controller. Is that not true?
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Permalink Reply by Martin Herzfeld on
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For you, if there is electric service where you are, Deep's solution is elegant. The power "loss" with the use of batteries > power "loss" when you loose the batteries.
Alexandra, suggest learning with a solar shade analysis tool for an accurate estimate. That's step one, are we done :-) ? Enjoyed chatting with you - let's give the gift that keeps on giving.
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Permalink Reply by Martin Herzfeld on
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In the meantime, let me elaborate on the answer. Your question briefly, directly and for you in English by a thesis, antithesis, synthesis, and emphasis :)
"Someone told me if you get shade on one panel then the one that is in full sun stops making power - so not to run them in series and go parallel into the mppt charge controller. Is that not true?"
Best practices would be for modules modules in series to maximize V(oc). When specifically, for a factors for Crystalline and Multicrystalline Silicon Modules are partially shaded results in substantial power loss. Although thin film provides some shade mitigation, would not be suggested, because the area of the modules increases and other factors - but may be an option. But if thin film, there typically more modules in parallel than series anyway based on the V(oc). But remember there will always be shade, the question is at what time. If DC-DC optimization cost of the system would increase.
Depending on the location of the array, the entire array would be shaded eventually anyway, and the time in which the array is shaded is before twilight and the power is decreased when shaded. When the voltage is decreased by modules in parallel, voltage drop increases, and when the conductors are a distance from the controller, the resistance increases and the voltage drop increases as a result the cost of the conductors and size increases. If the entire array is shaded, then the modules are in series or parallel would be shaded. If the array is shaded, between, for instance, 9am and 3 pm, the installation probably should have not proceeded - at solar noon at the zenith maximum power. Therefore, the location would not be a likely candidate for solar anyway. Remember no sun, no fun. The value of energy based on time is also a factor. Therefore, "wiring your solar panels in series or parallel is not going to make a difference in your performance loss due to shading"
There are other issues also with regards to the voltage of the array and the power loss of the balance of systems. The size of batteries and how there wired is a factor. If battery backup grid interactive or off grid, suggest a package system. Enphase would be for grid interactive, for the moment.
Explication of construction:
The question is one of impossible semantics. The answer is but true, but shouldn't be. In other words, impecunious - poor - putting a costly battery based systems in the shade around solar noon at maximum power with larger costly conductors including the maintainability of the batteries along with power losses for using batteries anyway compared to a simple grid interactive system seems wrong.
Emphasis:
Simply, if available, suggest micro-inverters or macro-inverters grid tied with Maximum Power Power Tracking (MPPT) in sunlight.
